1. Field of the Invention
This invention relates in general to saw guides, and in particular to a portable saw guide for use with hand power saws.
2. Description of Related Art
Making an accurate, smooth cut in a workpiece with a hand held power saw has been a long standing problem. The very portability of the hand power saw, with its ability to be carried to a workpiece, limits itself since it has no precise path defined for passing through a workpiece. Some of the prior art teaches a conversion of the saw into a non-hand held power saw, closely approximating a radial arm saw, table saw or the like, but in so doing it loses its very portability.
Other prior art teaches a device which attaches to the hand power saw, but in all cases the attached guide must project beyond the shoe plate of the saw in some fashion, thus limiting its use in certain applications.
This invention relates to prior art which teaches a separation of the guide from the hand power saw, so leaving the saw itself completely unencumbered for freehand cuts if desired. In each of the prior art cases, there are problems which have not been resolved, especially for cuts of 90 degrees and 45 degrees in long, wide boards of the type used in deck construction, decorative herringbone wall construction, and the like. Also, there have been problems in determining the cut line of a saw. In order to provide background information so the invention may be completely understood and appreciated, reference may be made to a number of prior art patents as follows:
U.S. Pat. No. 4,054,077 to R. H. Gram discloses a guide which is specifically designed for 90 degree and generally 45 degree cuts and is adequate for such, however the design is such that a workpiece being cut leans against a longitudinally sliding workpiece guide which is mounted in the center of a saw guiding platform. Thus, the available guiding surface for a saw is generally half the width of the saw guiding platform, and the guiding platform itself must be generally twice as wide as a workpiece being cut, thus the device must be generally twice as wide as is necessary, becoming less portable and more awkward to use. In addition, since a workpiece leans against only one workpiece guide, the free hand of the operator must grasp the workpiece and hold it in position both laterally and longitudinally to prevent movement of the device during a cut. While somewhat awkward, this can be accomplished, as long as the operator's free hand is dextrous enough to do it, but an operator with limited mobility who is unable to grasp the workpiece could not use this device without limiting its portability.
U.S. Pat. No. 3,516,457 to S. Winters discloses a guide which is designed for 90 degree and generally 45 degree cuts, and which shows a variation to allow swiveling of the guiding platform in relation to the workpiece guide, to make various mitered cuts. This device is adequate to accomplish its desired purpose, however it embodies the same two problems addressed in U.S. Pat. No. 4,054,077 above. In addition, it does not embody a kerf index or gauge of any kind.
U.S. Pat. No. 4,306,479 to J. F. Eberhardt discloses a guide which is designed for 90 degree cuts, and is adequate for such, however it is not designed for 45 degree cuts. Also, while a semi-dextrous or non-dextrous free hand may be able to hold the device in position, it was not designed for this, and slippage would probably result. Additionally, while the device incorporates a kerf gauge, the gauge is attached to the device with screws, so is not readily swapped with different size gauges if working with saws of different shoe plate widths, different size blades, or different blade tilts.
U.S. Pat. No. 4,494,434 to R. W. Young and U.S. Pat. No. 4,056,028 to G. K. Patterson both disclose devices which guide 90 degree cuts, with modifications to accomplish miter cuts up to 45 degrees. Both are portable, appear easy to use, and contain kerf gauges, however these devices must be firmly grasped and held in position with a dextrous hand necessitating the use of the thumb. Also, if the workpiece is especially wide, the thumb would not be able to reach far enough to hold the devices in position, which could result in slippage. In addition, these devices were designed to be used by a right handed person, or different versions could be made for a left handed person, but they could not be used by both left and right handed persons. Also, U.S. Pat. No. 4,494,434 embodies a kerf gauge housing for receiving a retractable kerf gauge, which also serves as a guiding edge, which extends further beyond the workpiece than is necessary for simply guiding the power saw. This same device also embodies a number of complex curves and shapes in its parts which would make it more difficult and expensive to manufacture.
U.S. Pat. No. 3,124,175 to D. E. McCloud discloses a device which was primarily designed to guide 90 degree and 45 degree cuts, and firmly hold the workpiece in position during the cut. This device is adequate to perform this function, however the device completely encircles the workpiece, and would be awkward to use for mid cuts on long boards, especially during multiple mid cuts, which would require repetitively sliding the device over the end and along the board into position, thus wasting much time. Also, the clamping means to hold the workpiece in position consists of two opposing wedges which, being separate from the main body of the device, could be misplaced, lost, or dropped and damaged, especially during busy worksite construction. Also, this device incorporates a central sheet, sandwiched midway between the opposing U-shaped and triangular surfaces, which provides strength, but limits the workpiece to being placed on only one side of the central sheet, thus the device must be constructed generally twice the thickness of the thickest workpiece to be used, thus making the device at least twice as thick as necessary. In addition, this device does not embody a kerf index or gauge of any kind.
There are many other devices which accomplish similar results, but the above cited references come closest to the intent of the invention. Whatever their precise merits, features and advantages, none of them achieves or fulfills the purposes of the present invention.